1. Field of the Invention
The invention is in the field of closed cycle thermal machines that use gas as a working substance and are applicable as either a refrigerator or an external combustion heat engine.
2. Description of the Related Art
One purpose of the invention is to provide an efficient refrigerator that uses an environmentally harmless, non-inflammable and non-toxic refrigerant, in order to overcome drawbacks of vapor compression refrigerators that are in common use. Vapor compression refrigerants are generally HFCs or hydrocarbons such as isobutane, both of which are objectionable; HFCs because of environmental effects and hydrocarbons because they are inflammable. Considered as a thermodynamic cycle, vapor compression refrigeration has two intrinsic sources of inefficiency, neither of which exist in the invention. One is that compressed vapor reaches a temperature much higher than ambient temperature, and then is cooled to near ambient temperature in a thermodynamically irreversible process that lowers efficiency. Secondly, expansion of warm liquid to cold vapor in a capillary or expansion valve sacrifices potentially recoverable expansion work.
Another purpose of the invention is to provide an efficient external combustion engine using the same configuration as is capable of refrigeration according to the earlier stated purpose of the invention.